Wolfram

A metallic element. Atomic number 74. Steel gray or silvery-white, high hardness, high melting point, room temperature from air attack; main purpose is to create the filament and high-speed cutting steel, hard mold, also used in optical instruments, chemical instrumentation tungsten; wolfram - element symbols W
     Overview: Tungsten belongs to non-ferrous metals, is also an important strategic metal, tungsten ore in ancient times was known as the "heavy stone." 1781 by the Swedish chemist Carl. William. She Yeer discovered scheelite, and extract the new elements acid - acid, in 1783 by the Spanish Air Asia discovery wolframite Depp also extract the acid, the same year, with the carbon reduction of tungsten trioxide first got tungsten powder, and named the element. Tungsten content in the crust is 0.001%. tungsten carbide inserts minerals have been found 20 species. Tungsten deposits generally accompanied by granitic magma activity and the formation. After smelting tungsten is a silvery white lustrous metal, high melting point, hardness greatly.
     Nature: Tungsten is a rare refractory metals, belonging to the sixth cycle of the periodic table (the second longest cycle) of the Group VIB. Tungsten is a silvery-white metal that looks like steel. Tungsten high melting point, low vapor pressure, the evaporation rate is smaller. Chemical properties of tungsten is very stable at room temperature when not react with air and water, without heating, any concentration of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia tungsten does not work when the temperature is raised to 80 ° -100 ° C, the various acids, except hydrofluoric acid, the other weak acid on the role of tungsten occur. At room temperature, the tungsten can be quickly dissolved in a mixture of hydrofluoric acid and nitric acid, but it does not work in an alkaline solution. With the presence of air, the molten base may be oxidized to tungsten tungstate in an oxidizing agent (NaNO3, NaNO2, KClO3, PbO2) in the presence of generated more violent reaction tungstate. Under high temperature and chlorine, bromine, iodine, carbon, nitrogen, sulfur and other compounds, but not with a hydride.